This invention relates to loudspeakers, and in particular, to electro-acoustic devices of the voice coil variety with built in amplification.
The desire to build a single assembly containing a loudspeaker and an amplifier has existed since the birth of audio electronics. Early attempts focused on creating lighter weight portable combination chassis units that could be placed anywhere to provide amplified sound. This type of unit, in reality, was bulky and quite heavy due to then available technologies, and is exemplified by Michael in U.S. Pat. No. 2,812,382.
With the miniaturization of electronic components came the desire to mount an entire power amplifier and related circuitry on the frame of a speaker. One of many such types of implementation is disclosed by Johnson et. al., in U.S. Pat. No. 5,164,991. In the Johnson patent, the goal was to provide variable amplification so as to permit a number of different types of line level signals to be connected to the amplifier rather than addressing the miniaturization and compacting issues of design. Another example is outlined in U.S. Pat. No. 3,499,988, where the speaker frame provides an area for mounting an associated amplifier circuit. The resulting amplifier/speaker assembly is easily accessible for servicing while taking advantage of the speaker frame for heat sinking the miniature electronic components appropriately. However, the components are not self contained with in the loudspeaker itself, electromagnetic interference (EMI) radiating components cannot be easily shielded at low cost. In U.S. Pat. No. 4,625,328, Freadman provides a less fragile more bulky amplifier loudspeaker combination by enlarging the speaker frame and integrating a traditional adaptation of a thin type heat sink which relies on the motion of the diaphragm to generate airwaves to cool the heat sink/amplifier structure. However, once again there is no easy way to inherently shield EMI radiating components within the assembly provided.
Another similar but different approach was undertaken by Jordan in U.S. Pat. No. 5,097,513 where both the loudspeaker and amplifier, as well as the enclosure are placed at opposite ends of a reflex duct to improve cooling while increasing base response. But this and similar arrangements do not inherently provide a way of achieving near zero length wiring connections between the loudspeaker and the amplifier/driver circuitry, providing EMI shielding for any EMI radiating components or reducing manufacturing costs. More recently, assemblies have been built where one or more loudspeakers have been placed in an enclosure with amplification stages and in some cases include either an optical or wireless radio-frequency receiver. While the prior art addresses various combinations of known technical issues, none address, greatly reduce or actually eliminate the cost of building and manufacturing multiple assemblies, the cost associated with heat dissipating hardware, the need to shield electromagnetic radiating components, as well as, other related technical issues.